The present invention relates to an optical coupler and more specifically to a directional optical coupler that includes an electro-optic member having an index of refraction that can be varied by application of an electric field.
Optical couplers are well known devices used to direct light from one light source to a light receiving member. In a known variety of optical couplers a layer of material is used which changes its index of refraction upon application of an electric field. The change in the index of refraction of the material so used in the prior art devices causes the light that is transmitted therethrough to change direction. The material used in this variety of optical couplers is anisotropic and thus exhibits significant index of refraction changes in more than one crystal axis.
A directional optical coupler in the present invention includes an optical cell that is comprised of a pair of opposing optically transparent conductors and an index of refraction variable layer interposed between the two optically transparent conductors. The index of refraction variable used in an optical cell according to the present invention exhibits a significant index of refraction variation along only one crystal axis upon application of an electric field and a negligible or no change in the index of refraction in other crystal axes. Thus, a light that is displaced by an optical cell according to the present invention will not have a changed polarization vector.
A directional optical coupler according to the present invention may include one optical cell or two or more optical cells as described above disposed on a suitable substrate such as a glass substrate.
A directional optical coupler according to the present invention may be used in conjunction with a number of different conventional optical devices such as reflective separation multipliers as part of a multiplexer/demutiplexer device or a scanner.
In addition, an optical cell according to the present invention may be interposed between two planar waveguides in order to act as a switch to make tunneling possible or to prevent tunneling between the two planar waveguides so as to act as switch therebetween. Such an arrangement may then be used in a tunneling optical matrix to allow for switching of light between a plurality of planar waveguides.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.